As I said earlier FH hardly requires or prefers a particular mix of group members since characters are rarely pigeonholed into a "class", and because it's easy to tailor the campaign to suit the group.
That said, the ideal group for 'generic' D&D-style adventuring would probably be a 50/50 mix of normal fighters and spellcasters. You need the latter for access to Powers. But in FH that access comes with all sorts of, well, limitations, so you also need to have a bunch of more reliable and durable warriors in the mix. Conversely, the warriors will be useful in 90% of combat situations, but supporting them with a spellcaster can make them much more effective.